Reducing inconsistencies of FAHP in structural safety assessment of diversion tunnels

Abstract

The Fuzzy Analytic Hierarchy Process (FAHP) is an effective method for assessing risks and has great potential for assessing the structural safety of diversion tunnels. However, this type of professional assessment can become more complicated due to the presence of multiple factors that influence the safety of the tunnel. This complexity not only necessitates the establishment of a comprehensive index system but also introduces uncertainties related to inconsistencies in expert judgments and unknown expert weights in group decision-making process. To address these issues, this study proposed an improved FAHP method for the structural safety assessment of diversion tunnels. This method incorporates a proposed comprehensive index system and incorporates a preceding ordering process before pairwise comparisons in the questionnaire to enhance the consistency in expert judgment. The consistency and compatibility of expert judgment matrices are quantified using a distance vector rather than a single number, and a reasonable comprehensive weight is calculated based on the Dempster–Shafer (D–S) evidence theory. We applied this method to the structure safety assessment of the Houziyan hydropower station diversion tunnel and found an overall low risk for the tunnel, but significant issues were identified regarding lining crack. Furthermore, we conducted a comparative evaluation of the proposed method against other related methods, thereby demonstrating its high quality. The study contributes an improved FAHP method for the structural safety analysis of diversion tunnels and encourages the wider application of FAHP in more complicated systems.